The function f (x) = 2 (3)^x– 1 is graphed below. What's the domain of the
function?

The domain of the expression is all real numbers except those where the expression is undefined. In this case, there are no real numbers that make the expression undefined.

Interval notation:

(−∞, ∞) (- ∞, ∞)

Set notation by comprehension:

{x | x∈R}